March 11, 2013

Predicting Death In Heart Disease Patients

Researchers studying more than 3,500 patients with heart disease say the length of DNA strands can help predict life expectancy.

Scientists at the Intermountain Heart Institute at Intermountain Medical Center in Salt Lake City presented a new study March 9 at the American College of Cardiology's Annual Scientific Session in San Francisco, claiming they were able to predict survival rates among patients with heart disease.

The team said they used the length of strands of DNA found on the ends of chromosomes known as telomeres to determine whether someone had a greater chance of living a longer life or not.

Previous studies showed telomere length can be used as a measurement of age, but these findings suggested telomere length may also predict the life expectancy of patients with heart disease. The researchers from Intermountain Heart Institute at Intermountain Medical Center decided to test this out.

As people get older, their telomeres get shorter, until the cell is no longer able to divide. A shortened telomere is associated with age-related diseases like heart disease or cancer, as well as exposures to oxidative damage from stress, smoking, air pollution, or conditions like accelerated biologic aging.

"Chromosomes by their nature get shorter as we get older," said John Carlquist, PhD, director of the Intermountain Heart Institute Genetics Lab. "Once they become too short, they no longer function properly, signaling the end of life for the cell. And when cells reach this stage, the patient's risk for age-associated diseases increases dramatically."

He said they tested the DNA samples from over 3,500 heart attack and stroke patients during the study.

"Our research shows that if we statistically adjust for age, patients with longer telomeres live longer, suggesting that telomere length is more than just a measure of age, but may also indicate the probability for survival. Longer telomere length directly correlate with the likelihood for a longer life–even for patients with heart disease," said Dr. Carlquist.

For the study, the team used an archive of peripheral blood DNA samples collected from about 30,000 heart patients, with as much as 20 years of follow-up clinical and survival data.

"With so many samples and very complete electronic records, it's a unique resource," said Dr. Carlquist. "It's unmatched in the world, and it allows us to measure the rate of change in the length of a patient's telomeres over time rather than just a snapshot in time, which is typical for most studies."

She said she believes telomere length could be used in the future as a way to measure the effectiveness of heart care treatment.

"We can already test cholesterol and blood pressure of a patient to see how treatment is working, but this could give us a deeper view into how the treatment is affecting the body and whether or not the treatment is working," she added.

University of East Anglia scientists completed a 20-year study, measuring telomere length across the entire lifespan of an animal.

“We investigated whether, at any given age, their telomere lengths could predict imminent death,” David Richardson, the study's lead author, said. “We found that short and rapidly shortening telomeres were a good indication that the bird would die within a year.”

He said he believes this study could have ramifications for human senescence studies, but would be difficult to replicate on human subjects, mostly because it would take a long time to study a human lifespan.